On Sunday, Venezuelans will have a chance to change the fate of this major oil-producing nation. They will vote for a new president and congress in what may be the most important elections in the last three decades of democracy here.

``This is a monumental election. At stake is the political and economic system,'' says Rita Funaro at VenEconomy, a Caracas-based economic consulting firm.

``Many people saw the coup leaders as heroes. Now they're saying, `Let's give democracy one last chance,' '' she adds.

Venezuelans want a change. And for the first time since Venezuela opted for a democratic path in 1958, the candidates of the two dominant political parties are not leading the polls. ``Depending on who wins ... the country could be on the brink of a true multiparty democracy, a protectionist economy, or a military coup,'' an analyst says.

``The common motivational factor in Venezuelan society is for a profound change of reality; political changes, economic changes, and social changes,'' says a study by Consultores 21, a Caracas-based political and economic analysis firm. Out with corruption

With the removal of President Carlos Andres Perez last year under charges of malfeasance, 65 percent of Venezuelans surveyed by Consultores 21 say they reject what Mr. Andres Perez represents to them: corruption, rule by party elite, and economic reforms.

Corrupt government leadership has become the symbol for all the woes suffered by Venezuelans in recent years. ``Corruption is seen as the explanation for lack of well being, injustice, poverty, low salaries, rising living costs, and crime,'' the Consultores 21 report says.

On a central Caracas thoroughfare restricted to pedestrians, comments like those of Felipe Ramirez, a retired oil worker, are common: ``After 30 years of democracy and so much oil money, why have we accomplished so little? Where did all the money go?''

The anti-establishment candidate with a small but consistent lead in the polls is 77-year-old ex-President Rafael Caldera Rodriguez. Portraying himself as an ``honest man,'' Mr. Caldera has turned from the Social Christian (Copei) party he helped found, and from his conservative roots, to become the populist leader of a coalition of smaller left- and right-wing parties.

Caldera opposes the free-market reforms of Andres Perez. He supports more state control, less-decentralization of power, and favors privatization only on ``a case-by-case'' basis.

``Caldera is a dangerous economic nationalist, still living in the 1960s. He could drive the economy into the ground,'' warns a Western diplomat.

But a well-known Venezuelan businessman cautions that although Caldera may be ``living in the past'' he will not be guided by the parties who support him. ``He won't make significant policy changes and will work to build a coalition with the old ruling parties in Congress. That's where his contacts and ties are,'' the businessman says.

The two candidates in almost a dead heat for second place are pro-free market Copei party candidate Oswaldo Alvarez Paz and the leftist-populist Radical Cause candidate Andres Velasquez. Mr. Velasquez, elected governor of Bolivar state last December, generally shows a slight lead in the polls over Mr. Alvarez Paz. New party emerges

A new party, the Radical Cause won the mayoralty of Caracas last December, and Velasquez is expected to win Caracas in the presidential elections.

Alvarez Paz is portrayed by some analysts as a ``Bill Clinton'' candidate: young, charismatic, and pragmatic. Another advantage is a national party organization. But for many Venezuelans, surveys show, his platform does not offer enough change from Andres Perez.

Most polls show Caldera with an 8 to 10 point lead over Velasquez and Alvarez Paz. Claudio Fermin, the candidate of Andres Perez's Democratic Action party, is another 5 to 10 points behind. About 20 percent of those surveyed are undecided.

The uncertainty over the outcome has caused a run on dollars. People are stocking up on food for fear of riots or a coup. All schools were closed a week before the elections to reduce the potential for organized violent protests.

The Defense Minister Vice Admiral Radames Munoz Leon has promised the elections will be fraud-free and peaceful. There are plans to put 85,000 troops and police on the streets to protect polling stations.

Alexander Watson, US State Department assistant secretary for Inter-American affairs, flew to Caracas on Nov. 30 to deliver a message from President Clinton. ``I want to assure you that any interruption in the democratic process in Venezuela would have an immediate, inevitable impact and [would] chill ... our bilateral relations,'' Mr. Watson said.

``If Velasquez wins, we could see violence,'' says Ms. Funaro, echoing a common theory. ``If the military doesn't move against him, the politicians may try to block his taking power by saying his candidacy was illegal because he didn't resign as governor first. The people would pour down from barrios in the hills to support him.''